Recorder



ug- 11 1964 R. P. BROWN ETAI. 3,143,940

RECORDER Original Filed Sept. 14, 1959 Hal United States Patent() 3,143,940 v RECORDER Richard P. Brown, Monrovia, and .lohn H. Jacobs, Altadena, Calif., assignors to Consolidated Electrodynamics Corporation, Pasadena, Calif., a corporation of California Original application Sept. 14, 1959, Ser. No. 839,617-

Divided and this application Nov. 15, 1960, Ser. No.v

The present invention relates to the eld of recording on printout material and, more specitically, relates to the vrapid latensiication of such material without fogging.

This application is a division of co-pending application Serial No. 839,617, tiled September 14, 1959, of Richard P. Brown and John H. Jacobs, now abandoned.

Materials which carry a photosensitive emulsion on one surface, such that an image recorded on the emulsion may be rendered visible by appropriate processing, are well-known. Such materials may have a variety of emulsion compositions. However, the basic constituents of such emulsions are a silver halide compound, usually in a matrix of gelatin. The silver halide compound is present in the form of crystals, usually triangular or hexagonal in configuration. The process by which an image is recorded by means of the silver halide crystals is not well-understood, even though this process, which is the basic process in photography, has been utilized for many years.

It has been found that rapid latensication without fogging of printout material can be accomplished by sub jecting .the exposed printout material emulsion to heat and subsequently exposing the printout material emulsion to electromagnetic radiations within a selected band of wave lengths. This statement, briefly, described the present invention, and the following theoretical discussion is made in an effort to explain the mechanism of operation of the invention as it is presently understood. The recording process consists of a building up of specks of silver atoms about certain locik on the silver halide crystal as a result of exposure of the crystal to electromagnetic radiations. The band of electromagnetic radiation wave lengths which are operable to initiate such a build-up is hereinafter refered to as the original recording sensitivity of the material.`

The following theoretical premises are made in order Vto provide a basicftheory upon which to base an explanation of the invention. A site which acts as the `locus of a build-up of silver on the silver halide crystal apparently Vconsists of a silver ion at aV discontinuity in the crystal lattice. This ion adsorbs a silver atom to become a latent pre-image speck. The speck is then built up by additional silver atoms to form a latent image speck. The latent pre-image speck has a comparatively short lifetime, whereas the latent image Vspeck exhibits stable existence. The lifetime of the latent pre-image speck is dependent upon the temperature ofthe emulsion. Elevation of the emulsion temperature decreases the lifetime of the latent pre-image speck. Unless the latent pre-image speck adsorbs an additional silver atom, therebybecoming a latent .sub-image speck, the latent ,pre-image speck dissociates into a silver atom and a silverV ion. The latent sub-image speck, consisting of two silver atoms adsorbed by a silver ion, is heat-stable; that is, the elevation Vof the temperature of the emulsion does not cause the latent subimage speck to dissociate into silver atoms and a silver ion. However, these latent sub-image specks are not developable as such. Rather, the silver atom content of the Yspeck must increase in ynumberso that the speck reaches a developable size,ki.e., becomes a ,latent image kCC speck. Latent image specks, like latent sub-image specks, are heat-stable.

For a given radiation wave length within the original recording sensitivity of the material, the number of such latent image specks which result upon exposure to the radiation is roughly proportional to the product of the intensity and duration of the exposure. This relationship is known as the reciprocity law. However, for a particular material, this process of producing latent image specks has a maximum etciency at a certain intensity of radiation. At intensity levels either greater or less than this intensity, the process is less efficient and results in a deviation from the reciprocity law which is known as reciprocity law failure. At recording exposures which utilize an exposure in the high-intensity reciprocity failure region, apparently a large number of latent sub-image specks result on the silver halide crystals during the recording exposure, rather than latent image specks.

So long as the silver halide crystals remain in existence as crystals, the image is said to be a latent image. The latent image is developed by the reduction of those silver halide crystals which contain latent image specks to metallic silver (chemical development); or the deposition on those crystals containing latent image specks of silver not directly derived from the silver halide crystal, which `deposition is dependent upon the number of latent image specks on the silver halide crystal (physical development). ln addition, the recording. radiations may themselves actually decompose the silver halide crystal so as to produce a metallic silver deposit at the latent image speck site (photolysis).

Recording materials are wellknown which make use of various combinations of chemical and physical development and photolysis in order to make the record itself visible soon after the actual act of recording. Recording exposures in the high-intensity reciprocity failure region are utilized with materials of this type in high speed oscillography. These materials are comparatively insensitive to radiations within the original recording sensitivity of the materials which are of low intensity, as are found in ambient lighting, for example. The recorded image is itself made visible by the action of material already in the emulsion, which is usually activated by exposure of the material to electromagnetic radiations. These materials do not require the subsequent application of a developing solution to render the image visible. Such recording materials are known as printout materials or printout papers.

Some early efforts relating to the use of printout materials to produce a continuous visible record of information are illustrated in the following patents:

German Patent No. 872,155 German Patent No. 880,496 U.S. Patent No. 2,580,427

The process by which the recorded image is made visible on printout materials by the exposure of the material to electromagnetic radiations is referred to, hereinafter, as latensifcation, although the actual process so designated embraces combinations of chemical and physical development of the latent image by materials already in the emulsion and photolysis of the silver halide crystals containing latent image'specks. The word latensication, as used hereinafter, is therefore not limited to the build-up of silver atoms at latent pre-image or sub-image specks to form latent image specks on silver halide crystals. The term access time-is used to indicate the time interval between the exposure of a photosensitive material to an electromagnetic recording radiation and the presentation 'of a visible record for observation. Conventionally, latensication of print-out materials is carried out at normal roomy lighting intensities. The latensification of g s 3 s printout materials by this sulted in access times in the range of magnitude of thirty or more seconds for latensification with satisfactory distintness of the record., p

' It is often desirable and even necessary to record information at printout material transport speeds in the order of magnitude of several inches per second so as to provide a useful record. In order to latensify the image recorded at such speeds, continuous exposure of the material to latensifying radiations for the thirty-second period is still necessary in conventional practice. Thus, it is 'readily apparent that the amount of printout material which must be exposed to light over any prolonged period at such speeds is so great as to have made impractical the use of such speeds heretofore.

Attempts to increase the rate of latensitication and thus reduce the access time of printout materials by utilizing higher latensifying radiation intensities have heretofore resulted in fogging of the material. Fogging of the printout material is caused bythe exposure of the material to high-intensity radiations within the original recording sensitivity of the material and the resulting formation of randomly distributed latent image specks. a lack of contrast to exist between the background of the printout material and the latent image corresponding to the recorded intelligence. Thus, the rate of latensification of printout materials heretofore could not satisfactorily be increased by subjecting printout materials to p latensifying radiations of higher intensity to give an access time of appreciably less than thirty seconds without foglging the record.

According to the present invention, the rapid latensication without fogging of printout materials to give access times of less than one second is accomplished by the latensilication of the printout material while its original recording sensitivity is inactive. Inactivation of the origi- .nal recording sensitivity of the printout material is accomplished by elevating the temperature of the pr1ntout maconventional method has re-Y Fogging causes faster rate when heated, so that new latent pre-image specks formed during latensiiication dissociate before adsorbing the additional silver atoms and ions required to constitute a stable speck for the formation of a latent image. The elevation of the emulsion temperature thus may inhibit the formation of latent sub-image specks from latent pre-image specks formed as a result of exposure of the printout material to the latensifying radiations, or it may actually prevent the formation of latent pre-image specks. In either event, the result is to inactivate the original recording sensitivity of the printout material. However, as was previously postulated, latent sub-image specks already existing as a result of the recording exposure are heat-stable at the temperatures contemplated by the invention. Exposure to the' latcnsifying radiations causes these latent sub-image specks to adsorb additional silver atoms and become latent image specks. As the latent image specks are also heat-stable, the process by which the latent image specks are latensified to form a visible image is not inhibited by heating the emulsion.

For certain printout materials, to preclude fogging in the practice of the invention, itis necessary to expose the printout material ,to the latensifying radiations during the period when the temperature of the emulsion of the material is elevated. For other materials, it is sufficient to elevate the temperature once, the temperature thereafter at whichlatensification occurs not normally being significant for the practice of this invention. It is not understood why the inactivation of the original recording sensitivity is permanent in one instance and temporary in the other.

The invention may be more readily understood by reference to the accompanying drawing in which:

FIGURE 1 is a sectional view of an apparatus for the recording and rapid latensification of printout material according to the invention; and

FIGURE 2 is a graphical representation of printout material sensitivity to electromagnetic radiations.

With reference to FIG. l, a recording oscillograph 11 has an outer case 12. A galvanometer mirror 13, connected to a galvanometer (not shown), reflects light directed thereon from a light source 14. The light source 14 may be, for example, a conventional mercury vapor point source commonly used in recording oscillographs. The light reiiected from the galvanometer mirror 13 passes through an aperture 15 in an inner dividing wall 16 of the oscillograph 11. Printout paper 17 contained in a roll 18 passes around a recording roller 19 positioned adjacent the aperture 15 so that the light reflected through the aperture 15 falls upon the printout paper 17. The printout paper 17 then passes around an idler roller 20 and onto a platen 21. The platen 21 contains heating means (not shown) operable to heat the platen 21 to a temperature which may be, for example, two hundred and fty degrees Fahrenheit. This heat is transferred to the printout paper 17 as it passes` over the platen 21 prior to exposure of the printout paper 1'7nto latensifrying radiations from a latensifying radiation source 22.

The latensifying radiation source 22 produces radiations which fall upon the printout paper 17 as it passes along the platen 21. After leaving the platen 21, the printout paper 17 is carried between a drive roller 24 and a second idler roller 25. These two rollers 24 and 25 provide the traction by means of which the printout paper 17 is unrolled from the roller 18 and passed along the path just described. Upon passing through the rollers 24 and 25,

the latensifying printout paper 17 issues from an aperture 27 in the oscillograph outer case 12 and is available for viewing, editing, and, if required, permanent fixing of the image.

It has been found that various types of printout mate rials exhibit latensication bands of differing widths. For example, the printout paper of one manufacturer exhibits a latensification band which extends from 2500 Angstrom units to 4700 Angstrom units, as is illustrated by solid line 30 and dotted line 31 in FIG. 2. The latensification band of the printout material of a second manufacturer extends from 2500 Angstrom units to 5700 Angstrom units, as is illustrated by line 30 and dotted line 32 in FIG. 2

In these printout materials, it has been found that there is a band of original recording sensitivity which fails generally between 3500 and 4300 Angstrom unit. The exact limits of the band are determined by the particular material. The latent sub image specks, at which points the latent image subsequently forms, result from the exposure of the particular portions of the printout material to electromagnetic radiations within the range of the original recording sensitivity of the material in a confiuration corresponding to the intelligence to be recorded.

Radiations beyond the upper limit of the latensification band, that is, the maximum value in Angstrom units of radiations which exhibit the characteristic of rapid latensification,V have been found to exhibit a deensitization effect when projected upon images recorded on printout materials prior to or during latensifcation. This desensitization effect apparently is a manifestation of the well-known Herschel effect, land is illustrated by dotted lines 33 and 34, for the papers of the first and second manufacturers referred to above, respectively, and solid line 35 in FIG. 2. The Herschel effect consists of the destruction of a latent image formed by electromagnetic radiations of a certain wave length by subjecting the latent i image to radiations of an appreciably longer wave length. Although the Herschel eiect is not particularly strong in most printout materials, the upper limit of the radiations useful for latensication apparently is defined by the radiation Wave length at which the etect commences to be manifested.v However, because latensification according to the invention is a high-intensity process and the Herschel effect is normally a low-intensity effect, the upper limit of latensifying radiations is not well-defined.

In practicing thel invention, for the printout materials currently available, heating of the platen 21 to a temperature in the order of magnitude of two hundred and fifty degrees Fahrenheit has the effect of inactivating the original recording sensitivity of the printout material. Of course, practice of the invention is not limited to the use of heated platens. A heated roller, or any other appropriate heat transfer means, can be used.

In certain types of printout papers, upon heating, the inactivation of the original recording sensitivity is permanent, whereas, in others, the inactivation process has been found to be reversible so that inactivation is only temporary. In the practice of the inventionafte'r the elevation of the temperature of the printout material, the material is exposed to the latensifying electromagnetic radiations and latensiiication occurs. In the type of printout material in which the inactivation of the original recording sensitivity is permanent, the printout material may be allowed to cool prior to its exposure to the latensifying radiations. However, such cooling normally does not occur in therpractice of the invention, inasmuch as allowing the printout material to cool is not consistent with the requirement of a rapid access time. In the type of printout material in which the inactivation of the original recording sensitivity only exists so long as the temperature of the material remains elevated, it is, of course, necessary to expose the material to the latensifying radiations While the temperature is so elevated, in order to avoid background fogging while practicing rapid latensilication according to this invention.

Inasmuch as the rapidlatensification of printout material is a novel process, data on the various printout materials with regard to the practice of this invention are not available. Therefore, it is necessary, with' respect to the various types of printout materials, to experimentally determine the original recording sensitivity range and the latensilication range of the material. The temperature required for inactivation of the original recording sensitivity and, if desired, Whether heating the material prior to latensication results in a permanent or only temporary inactivation of the original recording sensitivity, are also determined experimentally.

The determination of the original recording sensitivity and latensiiication ranges of a particular printout material is accomplished by irst recording intelligence on a strip of the printout material. Latensication is preferably made utilizing a white light source, so as to subject the printout material to radiations having a broad range of Wave lengths. The spectrum of the anticipated latensification range of the printout material in then spread out according to Wave length on the recorded material by means of a spectrograph. The width of the latensiiication band of the printout material is apparent from the printout material as corresponding to the Wave length band over which the recorded information has been latensied. The region of original recording sensitivity of the material then corresopnds to that portion which exhibits both latensication of the recorded intelligence and background fogging. In extreme cases, the fogging may obscure the image. In the region of the upper limit of the latensiiication band, the latensication effect is less pronounced. Due to manifestation of the Herschel effect in this region, latensication of the recorded image may not occur upon subsequent exposure of this portion of the material to radiations within the latensiication band.

Having determined the lower limit for latensication radiations, and the upper limit of the latensiiication radiations, i.e., the wave length at which the Herschel effect becomes signiicant, an appropriate latensifcation radiation source is selected by comparing radiation spectrurns for various available sources of radiation with the radiation spectrum required for rapid latensiiication of the printout material according to the invention. After determining the latensiication band of the printout material, and providing a suitable latensication radiation source, the temperature to which the material must be elevated in order to preclude fogging, by inactivating the original recording sensitivity of the material, is determined by trial and error method. A trial and error method is preferable in order to take into account the heat transfer characteristic of the particular heat transfer means utilized to elevate the temperature of the printout material and the transport rate of the material. If it is further desired to determine whether the original recording sensitivity of the material remains inactivated after having its temperature elevated, a portion of the material is allowed to cool prior to latensiication. If latensiiication of the cooled portion is accompanied by background fogging, the inactivation of the original recording sensitivity of the material upon heating is temporary rather than permanent.

The source chosen for the latensiiication radiations may emit signicant amounts of radiation beyond the upper limit of the latensication band. Whether or not these radiations are such as to degrade the quality of the latensied image must be determined experimentally for the particular radiation source and printout material. The latensication process usually becomes less eflicient in the region of the upper limit of the latensiiication band. This region may or may not overlap the region in which the Herschel effect normally becomes significant for the particular printout material. Thus, in the practicev of the invention, the upper limit of the latensii'lcation band is dened by that region beyond which, for the particular printout material and latensication spectrum utilized, additional radiations of longer wave length are not signiiicantly useful to produce latensication of the recorded image. However, the use of a latensifying radiation source emitting, in addition to radiations within the latensication band of the material, such additional radiations vof longer wave length, constitutes practice of the invention whether or not such longer wave length radiations actually produce any latensication of the recorded image.

We claim:

1. A device for rapidly latensifying images which have been recorded on printout material, comprising a source of heat, means for applying heat from said heat source to the printout material so as to heat the printout material to a temperature which substantially inactivates its original recording sensitivity without fogging the printout material, a source of latensifying electromagnetic radiations having wave lengths within the range of from about 2500 Angstrom units to that wave length at which the Herschel effect becomes signicant for the printout material and means for exposing the printout material to the latensifying radiations while the original recording sensitivity of the printout material is substantially inactive.

2. A device for rapidly latensifying images which have been recorded on printout material, comprising means for elevating the temperature of the printout material to a temperature which substantially inactivates its original recording sensitivity after the recording thereon of an image without fogging the printout material, a source of latensifying electromagnetic radiations having wave lengths within the range of from about 2500 Angstrom units to that wave length at which the Herschel effect becomes significant for the printout material, and means for exposing the printout material to the latensifying electromagnetic radiations subsequent to the elevation of the 7 printout material temperature while the original recording sensitivity of the printout material `is substantially inactive.

3. A device as dened in claim 2, in which the exposure means exposes the printout material to the latensifying electromagnetic radiations during the period of printout material temperature elevation.

4. A device for the rapid latensication of images recorded on printout material, comprising a source of recording electromagnetic radiations within the range of the original recording sensitivity of the printout material, means for exposing the printout material to the recording radiations, means for heating the printout material to a temperature which substantially inactivates its original recording sensitivity subsequent to its exposure to the recording radiations Without fogging the printout material, a source of latensifying electromagnetic radiations having Wave lengths within the range of from about 2500 Angstrom units to that wave length at which the Herschel effect becomes significant for the printout material, and means for exposing the printout material to the latensifying radiations While the originalrecording sensitivity of the printout material is substantially inactive.

5. A device for the rapid latensication of images recorded on printout material, comprising means for recording an image on the printout material by means of visible light, means for heating the printout material to a temperature which substantially inactivates its original recording sensitivity without fogging the printout material, and means for subsequently exposing the printout material to latensifying electromagnetic radiations having Wave lengths within the range of from about 2500 Angstrom units to that Wave length at which the Herschel ,e'ect becomes significant for the printout material While the original recording sensitivity of the printout material is substantially inactive.

6. A device for the rapid latensication of printout material comprising a source of recording electromagnetic radiations, means for projecting the recording radiations onto the printout material, a source of latensifying electromagnetic radiations having wave lengths within the range of from about 2500 Angstrom units to that wave length at which the Herschel effect becomes signicant for the printout material, means for projecting the latensifying electromagnetic radiations onto the printout material subsequent to the projection thereon of the recording radiations, and heat transfer means operable subsequent to recording and prior to latensification to heat the printout material to a temperature which substantially inactivates its original recording sensitivity Without fogging the printout material.

7. A device as dened in claim 6, yin which the eX- posure' of the printout material to the latensifying electromagnetic radiations occurs While the printout material is at a temperature which inactivates its original recording sensitivity.

8. A device for the rapid latensitication of printout paper contained on a roller comprising a source of recording electromagnetic radiations, a source of latensifying electromagnetic radiations having Wave lengths within .the range of from about 2500 Angstrom units to that wave length at which the Herschel eifect becomes signicant for the printout material, a source of heat positioned between the source of recording radiations and the source .of latensifying radiations, and means for causing the printout paper to pass in sequence adjacent the source of recording radiations, the source of heat, and the source of latensifying radiations, whereby the printout paper is heated subsequent to recording and prior to latensication to a temperature which substantially inactivates its original recording sensitivity Without fogging the printout paper.

9. A device as dened in claim 8, in which the eX- posure of the printout paper to the latensifying electromagnetic radiations occurs While the printout material is at a temperature which inactivates its original recording sensitivity. v

l0. A device for the rapid latensication of an exposed printout emulsion carried on a backing comprising a platen, means for passing the printout emulsion and backing over the platen so that the backing is in contact with the platen, means for heating the platen to a temperature such that upon passage thereon of the backing and emulsion, the emulsion is heated to a temperature Which substantially inactivates its original recording sensitivity without fogging, a source of latensifying radiations for wave lengths Within the range of wave lengths from about 2500 Angstrom units to about 5700 Angstrom units, and means for projecting the latensifying radiations upon the emulsion after it has been heated by passage over the platen and while its original recording sensitivity is substantially inactive.

References Cited in the iile of this patent UNITED STATES PATENTS 

1. A DEVICE FOR RAPIDLY LATENSIFYING IMAGES WHICH HAVE BEEN RECORDED ON PRINTOUT MATERIAL, COMPRISING A SOURCE OF HEAT, MEANS FOR APPLYING HEAT FROM SAID HEAT SOURCE TO THE PRINTOUT MATERIAL SO AS TO HEAT THE PRINTOUT MATERIAL TO A TEMPERATURE WHICH SUBSTANTIALLY INACTIVATES ITS ORIGINAL RECORDING SENSITIVITY WITHOUT FOGGING THE PRINTOUT MATERIAL, A SOURCE OF LATENSIFYING ELECTROMAGNETIC RADIATIONS HAVING WAVE LENGTHS WITHIN THE RANGE OF FROM ABOUT 2500 ANGSTROM UNITS TO THAT WAVE LENGTH AT WHICH THE HERSCHEL EFFECT BECOMES SIGNIFICANT FOR THE PRINTOUT MATERIAL AND MEANS FOR EXPOSING THE PRINTOUT MATERIAL TO THE LATENSIFYING RADIATIONS WHILE THE ORIGINAL RECORDING SENSITIVITY OF THE PRINTOUT MATERIAL IS SUBSTANTIALLY INACTIVE. 